1. Field of Invention
This invention is directed to a curable, acrylic polymer and to a composition, particularly a coating composition, containing an acrylic polymer which composition cures at low temperature, preferably ambient temperature, in the presence of moisture.
2. Description of Prior Art
U.S. Pat. No. 4,368,294 describes organopolysiloxane modified organic polymers prepared by reacting, in the presence of water in excess of any formad during the reaction, organic polymers containing C-bonded hydroxyl groups with organopolysiloxanes containing Si-bonded hydroxyl groups and/or alkyl groups which are bonded to silicon via oxygen. However, the polymers disclosed therein, as can be seen from the examples, are essentialy polymers which are cured by conventional means such as heat curing of C--OH groups on the polymers using a C--OH reactive crosslinking agent.
U.S. Pat. No. 4,339,261 describes a curable composition containing a blend of (a) a silyl-group containing vinyl resin which has a main chain consisting essentially of vinyl polymer and has in one molecule at least one silicon atom connected to a hydrolyzable group on the terminal or side chain; (B) a iin compound; and (C) an amine having in one molecule at least one silicon atom connected to a hydrolyzable group. Column 2, lines 6-20 discloses that the vinyl resin (A) contains a main chain consisting essentially of one or more hydrolyzable silyl groups attached to its terminal or side chains. It is specifically disclosed that the silyl group is represented by a specified formula (I) in which the silicon atom of the silyl group containing the hydrolyzable group is bound to the vinyl resin through a carbon linkage. Two methods are disclosed for preparing the silyl group containing vinyl resin of the patent.
The first involves the reaction of a hydrosilane with a vinyl resin having carbon-carbon double bonds in the presence of a complex of a Group VIII transition metal. The preparation of such silyl group containing resins by this first method is also described in U.S. Pat No. 4,191,713. The second method described in U.S. Pat No. 4,399,261 is for preparing the silyl group containing vinyl resin involves free radical copolymerization of a vinyl compound with a silane compound of specified formula having a polymerizable double bond therein, an example of the silane compound being gamma-methacryloxypropyltrimethoxysilane. However, the methods for preparing the silyl group containing vinyl resins, and hence the resins themselves, tend to be costly which thereby tends to effectively limit their utility. For example, compounds such as functional organosilane like gamma-methacrylatopropyl trimethoxy silane as well as platinum catalysts are costly. Moreover, compositions based on such resins often do not cure as well as is desirable for a number of purposes, and typically contain lower total solids contents than is desirable for a number of purposes. Additionally it is difficult to prepare in a reproducible manner such resins from monomers which contain active hydrogen atoms such as hydroxyl groups so as to obtain resins having relatively uniform properties.
3. Some Objects of the Present Invention
There is a continuing need, particularly in the coatings industry, to provide compositions which have low curing temperatures and, preferably, which cure at ambient temperature. There is also a continuing need to provide compositions which contain ever lower concentrations of volatile organic components. Additionally, it would be desirable to provide compositions which do not depend on organic isocyanates for curing.
However, previous approaches to meet these challenges generally have involved disadvantageous compromises among desirable coating composition properties such as molecular weight of the principal film forming resin, application viscosity of the composition, low curing temperature, and desirable properties of the cured film such as water resistance, flexibility, hardness, solvent resistance, etc.
Objects of the present invention are to help meet these challenges. Additionally, an object of the present invention is to prepare new curing agents for organic polyols. Other objects of the invention will become apparent to the reader infra.